Fuel economy

[RonD]

It is well known that carrying excess weight in the boot of your car etc can increase your fuel consumption. It occurred to me that filling the car with 40 litres of fuel (after getting a bank loan) will add almost six and a half stones, or another 88lbs in weight. This is like carrying around another passenger with the resultant increase in consumption. If the car is only filled to as much as the journey dictates, a mpg saving should be made. If a long journey is imminent then common sense must prevail.

Ron D

Ron

 

[RogerL]

But if everyone did that we'd have a glut of fuel, driving the price down - it's the exact opposite of panic buying.

The specific gravity of fuel is about 0.8 so 40 litres will weigh about 32 kg / 71 lbs.

Frivolity and pedantry aside, it's a point well made Ron.

 

[big john wayne]

Filling up with just enough for the journey would result in increased use and wear of the cars filler cap. This would in turn create panic buying of filler caps and , result in large ques outside of halfords .

 

[Gumbo]

I will need to work out the increase in fuel consupption in comparison to filling the car at tesco with 5p a litre off

coupon. This caravannings getting difficult.

good point though Ron

 

[Glenn_5132962]

Roy, it must be weighed up against the detour required to reach the petrol stn. My mate does exactly what you say but of the

 

[Gumbo]

Fuel consumption increases/decreases with the square of the speed - reducing from 60 to 56 will use 13% less fuel once you've got to cruising speed - as long as the engine remains in the torque band and stays in the same gear. Reducing the rate of acceleration will also help consumption considerably.

That's like a litre of diesel being reduced from

 

[ShadySadie]

Is lead free fuel more economomic than the old leaded fuel?

How much will I save if I can get back to a size 10 again? (need to lose about 8lbs)

Could fat people save the planet and stop fuel shortages if they and everyone else got down to their ideal BMI ?

 

[RogerL]

Fuel consumption increases/decreases with the square of the speed - reducing from 60 to 56 will use 13% less fuel once you've got to cruising speed - as long as the engine remains in the torque band and stays in the same gear. Reducing the rate of acceleration will also help consumption considerably.

That's like a litre of diesel being reduced from

 

[rob_jax]

Quote "Is lead free fuel more economomic than the old leaded fuel?"

Probably not - or maybe only a bit - but there are other factors...

Compared to modern lead-free fuel, leaded petrol wasn't a particularly well controlled or refined product - and the lead was added to boost the Octane number and stop the fuel "pinking" when burnt in the engine.

Modern lead-free petrol is a vastly different fuel - highly controlled and the "right" Octane number is produced by chemically modifying the base fuel rather than by adding an additive - so it's right to begin with...

The difference in economy is in the engine technology that the two fuels support - computer controlled highly accurate, multi-point petrol injection for unleaded, rather than the old rough and ready carburettor...

Mind you some of those significant gains were lost when the exhaust catalyst was added - these must receive a closely controlled fuel / air mixture from the engine - and this isn't the optimum mixture for maximum economy (but quite close).

Robert

 

[ShadySadie]

Quote "Is lead free fuel more economomic than the old leaded fuel?"

Probably not - or maybe only a bit - but there are other factors...

Compared to modern lead-free fuel, leaded petrol wasn't a particularly well controlled or refined product - and the lead was added to boost the Octane number and stop the fuel "pinking" when burnt in the engine.

Modern lead-free petrol is a vastly different fuel - highly controlled and the "right" Octane number is produced by chemically modifying the base fuel rather than by adding an additive - so it's right to begin with...

The difference in economy is in the engine technology that the two fuels support - computer controlled highly accurate, multi-point petrol injection for unleaded, rather than the old rough and ready carburettor...

Mind you some of those significant gains were lost when the exhaust catalyst was added - these must receive a closely controlled fuel / air mixture from the engine - and this isn't the optimum mixture for maximum economy (but quite close).

Robert

I just thought there may have been a weight saving using "UNLEADED" ;-)

 

[Gumbo]

It was me, not John L !!

Sorry Roger

It looks right under this heading

 

[RogerL]

Each set of Euro n? emission regulations seem to make fuel consumption worse. A number of cars where most economical in the era of unleaded fuel but without catalytic converters.

As an obsession to get rid of CO, which was naturally converted to CO2 in the atmosphere, we now create more CO2 than we used to.

 

[RonD]

Robert,

A question asked in my local paper... If CO2 is heavier than air, how does it get up into the atmosphere to cause 'greenhouse gas' problems?

 

[rob_jax]

Ron,

The answer is "because we are all alive" - if gasses really did form distinct layers in the atmosphere - then CO2 would be at the bottom and we'd all be dead, then a thick layer of Nitrogen and we'd still be dead, and a thinner layer of Oxygen on top of that - starting way above the level where jets fly...

So since we're all alive, gasses don't naturally form layers - they mix - in the same way that table salt dissolved in a glass of water tastes salty all the way down...

LPG - but you'll say "caravans have drop out vents for (heavy) LPG gas" - and that's true, but that's because any gas leak is a pure, concentrated stream of gas that hasn't yet had a chance to mix with the surrounding air.

A gas leak is like making Irish Coffee - you can carefully pour the cream as a separate layer on the coffee, but once stirred with a spoon - it's evenly distributed and doesn't reform as a layer.

OK - this is not entirely true - there is a gravitational partition of gasses in the atmosphere - but the effect is small.

Robert

 

[RonD]

Thanks for that Robert, an excellent explanation.